<!DOCTYPE html>
<html lang="zn-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒子</title>
    <style>
        div {
            height: 200px;
            width: 200px;
            border: blue solid 5px;
            border-top: red solid 5px;
            
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>